DirectX 8.1 shipped as an integral part of
Windows XP and is available for all versions of Windows 98, Windows ME and Windows
2000. Developers choosing to support Windows 95 should continue to use DirectX
8.0a.

DirectX 8.1 includes all of the previous DirectX
8.0 functionality as well as new DirectX graphics features and new DirectShow
features specific to Windows XP.

DirectX 8.1 graphics supports the following
new features:

new pixel shader models
1.2, 1.3, and 1.4

new high precision texture
formats

new nPatch quadratic interpolation
order

new dynamic texture support

new D3DX methods

updated DirectX graphics
documentation

There have been considerable improvements made
to the DirectShow content for the DirectX 8.1 SDK. These improvements include
updating existing samples, adding many new samples (including Windows XP samples),
providing modified source code for the sampleGrabber, and improving documentation.
See the DirectShow section below for more specific information.

The SDK contains several new tools, they include:

screensaver framework

AppWizard support

DX error lookup tool

MView mesh viewer

DP8sim network simulator

This DirectX 8.1 version of DirectMusic Producer
sports a number of new features to streamline the authoring process for composers
and sound designers. Some of these features include low enough software synthesizer
latency to input musical performances from a keyboard in real time (WDM driver
required), easier wave capture, and improved DLS/wave editing features like
one-click stereo wave insert, insert silence and a resample wave option. Segment
Designer features include multiple wave insert as segments, the ability to edit
segment length based on clocktime, and ability to start and stop segments while
editing DMO effects. Other improvements include many bug fixes, an improved
look to segment strips and customizable wallpaper. Documentation has been thoroughly
revamped and a new tutorial with a sample game is also available.

DirectX 8.0a Information:

DirectX 8.0a contains updates for issues with
international installs on Windows 2000 and issues where input devices could
have buttons disabled that were enabled with previous DirectX releases. There
are no other changes.

DirectX 8.0:

There are many new features in DirectX 8 that
makes this a worthwhile upgrade.

Consolidated interfaces
for DirectDraw® and Direct3D® simplify application development
and improve performance.